The overall goal of the proposed research is to investigate psychological and behavioral mechanisms that may be responsible for white coat hypertension. Based on the evidence from clinical observation studies, as well as the clear parallels to a vast psychology literature, or primary focus will be on stress and classical conditioning. To explore the possible roles of stress and classical conditioning in white coat hypertension, we propose a program of research that combines three complementary studies: 1) a longitudinal correlational study of relations between psychobehavioral variables and white coat hypertension; 2) an experimental study of cardiovascular responses to laboratory models of stress and conditioning; 3) a controlled clinical study of two experimental manipulations based on stress and classical conditioning theory. Three groups (n=150/group) of subjects (50% women) will be recruited: a) individuals clinically identified as having white coat hypertension (WCHT-Group), b) individuals clinically identified as having moderate established hypertension (EH-Group), c) individuals identified as being normotensive (NT-Group). Specific Aim 1: To investigate the relationships between white coat hypertension and psychological, and behavioral factors derived from stress and classical conditioning theory. Specific Aim 3: To test the causal relations between stress and classical conditioning predictors of white coat hypertension. The proposed research will be the first to concurrently investigate the contributions of stress and classical conditioning to the phenomenon of white coat hypertension. A greater understanding of those mechanisms may help provide guidance for the development of effective interventions with this population, including specific psychobehavioral interventions. Furthermore, the program of research may help to clarify the conflicting literature concerning potential pathogenic consequences of white coat hypertension.